/*
 * An implementation of what I call the "Sea of Stars" algorithm for
 * POSIX fnmatch(). The basic idea is that we factor the pattern into
 * a head component (which we match first and can reject without ever
 * measuring the length of the string), an optional tail component
 * (which only exists if the pattern contains at least one star), and
 * an optional "sea of stars", a set of star-separated components
 * between the head and tail. After the head and tail matches have
 * been removed from the input string, the components in the "sea of
 * stars" are matched sequentially by searching for their first
 * occurrence past the end of the previous match.
 *
 * - Rich Felker, April 2012
 */

#include <string.h>
#include <fnmatch.h>
#include <stdlib.h>
#include <wchar.h>
#include <wctype.h>
#include "locale_impl.h"

#define END 0
#define UNMATCHABLE -2
#define BRACKET -3
#define QUESTION -4
#define STAR -5

static int str_next(const char *str, size_t n, size_t *step)
{
    if (!n) {
        *step = 0;
        return 0;
    }
    if (str[0] >= 128U) {
        wchar_t wc;
        int k = mbtowc(&wc, str, n);
        if (k<0) {
            *step = 1;
            return -1;
        }
        *step = k;
        return wc;
    }
    *step = 1;
    return str[0];
}

static int pat_next(const char *pat, size_t m, size_t *step, int flags)
{
    int esc = 0;
    if (!m || !*pat) {
        *step = 0;
        return END;
    }
    *step = 1;
    if (pat[0]=='\\' && pat[1] && !(flags & FNM_NOESCAPE)) {
        *step = 2;
        pat++;
        esc = 1;
        goto escaped;
    }
    if (pat[0]=='[') {
        size_t k = 1;
        if (k<m) if (pat[k] == '^' || pat[k] == '!') k++;
        if (k<m) if (pat[k] == ']') k++;
        for (; k<m && pat[k] && pat[k]!=']'; k++) {
            if (k+1<m && pat[k+1] && pat[k]=='[' && (pat[k+1]==':' || pat[k+1]=='.' || pat[k+1]=='=')) {
                int z = pat[k+1];
                k+=2;
                if (k<m && pat[k]) k++;
                while (k<m && pat[k] && (pat[k-1]!=z || pat[k]!=']')) k++;
                if (k==m || !pat[k]) break;
            }
        }
        if (k==m || !pat[k]) {
            *step = 1;
            return '[';
        }
        *step = k+1;
        return BRACKET;
    }
    if (pat[0] == '*')
        return STAR;
    if (pat[0] == '?')
        return QUESTION;
escaped:
    if (pat[0] >= 128U) {
        wchar_t wc;
        int k = mbtowc(&wc, pat, m);
        if (k<0) {
            *step = 0;
            return UNMATCHABLE;
        }
        *step = k + esc;
        return wc;
    }
    return pat[0];
}

static int casefold(int k)
{
    int c = towupper(k);
    return c == k ? towlower(k) : c;
}

static int match_bracket(const char *p, int k, int kfold)
{
    wchar_t wc;
    int inv = 0;
    p++;
    if (*p=='^' || *p=='!') {
        inv = 1;
        p++;
    }
    if (*p==']') {
        if (k==']') return !inv;
        p++;
    } else if (*p=='-') {
        if (k=='-') return !inv;
        p++;
    }
    wc = p[-1];
    for (; *p != ']'; p++) {
        if (p[0]=='-' && p[1]!=']') {
            wchar_t wc2;
            int l = mbtowc(&wc2, p+1, 4);
            if (l < 0) return 0;
            if (wc <= wc2)
                if ((unsigned)k-wc <= wc2-wc ||
                    (unsigned)kfold-wc <= wc2-wc)
                    return !inv;
            p += l-1;
            continue;
        }
        if (p[0]=='[' && (p[1]==':' || p[1]=='.' || p[1]=='=')) {
            const char *p0 = p+2;
            int z = p[1];
            p+=3;
            while (p[-1]!=z || p[0]!=']') p++;
            if (z == ':' && p-1-p0 < 16) {
                char buf[16];
                memcpy(buf, p0, p-1-p0);
                buf[p-1-p0] = 0;
                if (iswctype(k, wctype(buf)) ||
                    iswctype(kfold, wctype(buf)))
                    return !inv;
            }
            continue;
        }
        if (*p < 128U) {
            wc = (unsigned char)*p;
        } else {
            int l = mbtowc(&wc, p, 4);
            if (l < 0) return 0;
            p += l-1;
        }
        if (wc==k || wc==kfold) return !inv;
    }
    return inv;
}

static int fnmatch_internal(const char *pat, size_t m, const char *str, size_t n, int flags)
{
    const char *p, *ptail, *endpat;
    const char *s, *stail, *endstr;
    size_t pinc, sinc, tailcnt=0;
    int c, k, kfold;

    if (flags & FNM_PERIOD) {
        if (*str == '.' && *pat != '.')
            return FNM_NOMATCH;
    }
    for (;;) {
        switch ((c = pat_next(pat, m, &pinc, flags))) {
        case UNMATCHABLE:
            return FNM_NOMATCH;
        case STAR:
            pat++;
            m--;
            break;
        default:
            k = str_next(str, n, &sinc);
            if (k <= 0)
                return (c==END) ? 0 : FNM_NOMATCH;
            str += sinc;
            n -= sinc;
            kfold = flags & FNM_CASEFOLD ? casefold(k) : k;
            if (c == BRACKET) {
                if (!match_bracket(pat, k, kfold))
                    return FNM_NOMATCH;
            } else if (c != QUESTION && k != c && kfold != c) {
                return FNM_NOMATCH;
            }
            pat+=pinc;
            m-=pinc;
            continue;
        }
        break;
    }

    /* Compute real pat length if it was initially unknown/-1 */
    m = strnlen(pat, m);
    endpat = pat + m;

    /* Find the last * in pat and count chars needed after it */
    for (p=ptail=pat; p<endpat; p+=pinc) {
        switch (pat_next(p, endpat-p, &pinc, flags)) {
        case UNMATCHABLE:
            return FNM_NOMATCH;
        case STAR:
            tailcnt=0;
            ptail = p+1;
            break;
        default:
            tailcnt++;
            break;
        }
    }

    /* Past this point we need not check for UNMATCHABLE in pat,
     * because all of pat has already been parsed once. */

    /* Compute real str length if it was initially unknown/-1 */
    n = strnlen(str, n);
    endstr = str + n;
    if (n < tailcnt) return FNM_NOMATCH;

    /* Find the final tailcnt chars of str, accounting for UTF-8.
     * On illegal sequences we may get it wrong, but in that case
     * we necessarily have a matching failure anyway. */
    for (s=endstr; s>str && tailcnt; tailcnt--) {
        if (s[-1] < 128U || MB_CUR_MAX==1) s--;
        else while ((unsigned char)*--s-0x80U<0x40 && s>str);
    }
    if (tailcnt) return FNM_NOMATCH;
    stail = s;

    /* Check that the pat and str tails match */
    p = ptail;
    for (;;) {
        c = pat_next(p, endpat-p, &pinc, flags);
        p += pinc;
        if ((k = str_next(s, endstr-s, &sinc)) <= 0) {
            if (c != END) return FNM_NOMATCH;
            break;
        }
        s += sinc;
        kfold = flags & FNM_CASEFOLD ? casefold(k) : k;
        if (c == BRACKET) {
            if (!match_bracket(p-pinc, k, kfold))
                return FNM_NOMATCH;
        } else if (c != QUESTION && k != c && kfold != c) {
            return FNM_NOMATCH;
        }
    }

    /* We're all done with the tails now, so throw them out */
    endstr = stail;
    endpat = ptail;

    /* Match pattern components until there are none left */
    while (pat<endpat) {
        p = pat;
        s = str;
        for (;;) {
            c = pat_next(p, endpat-p, &pinc, flags);
            p += pinc;
            /* Encountering * completes/commits a component */
            if (c == STAR) {
                pat = p;
                str = s;
                break;
            }
            k = str_next(s, endstr-s, &sinc);
            if (!k)
                return FNM_NOMATCH;
            kfold = flags & FNM_CASEFOLD ? casefold(k) : k;
            if (c == BRACKET) {
                if (!match_bracket(p-pinc, k, kfold))
                    break;
            } else if (c != QUESTION && k != c && kfold != c) {
                break;
            }
            s += sinc;
        }
        if (c == STAR) continue;
        /* If we failed, advance str, by 1 char if it's a valid
         * char, or past all invalid bytes otherwise. */
        k = str_next(str, endstr-str, &sinc);
        if (k > 0) str += sinc;
        else for (str++; str_next(str, endstr-str, &sinc)<0; str++);
    }

    return 0;
}

int fnmatch(const char *pat, const char *str, int flags)
{
    const char *s, *p;
    size_t inc;
    int c;
    if (flags & FNM_PATHNAME) for (;;) {
        for (s=str; *s && *s!='/'; s++);
        for (p=pat; (c=pat_next(p, -1, &inc, flags))!=END && c!='/'; p+=inc);
        if (c!=*s && (!*s || !(flags & FNM_LEADING_DIR)))
            return FNM_NOMATCH;
        if (fnmatch_internal(pat, p-pat, str, s-str, flags))
            return FNM_NOMATCH;
        if (!c) return 0;
        str = s+1;
        pat = p+inc;
    } else if (flags & FNM_LEADING_DIR) {
        for (s=str; *s; s++) {
            if (*s != '/') continue;
            if (!fnmatch_internal(pat, -1, str, s-str, flags))
                return 0;
        }
    }
    return fnmatch_internal(pat, -1, str, -1, flags);
}
